The corpus striatum (caudate nucleus, putamen, and globus pallidus) plays an important role in coordinating and patterning movement. Damage to the striatum in humans, such as occurs in Huntington's chorea in Parkinson's or Wilson's diseases, produces profound and complex behavioral disruptions. Current hypotheses of striatal function have suggested the corpus striatum patterns action by contributing to (a) the initiation and execution of centrally-programmed ("player-piano") sequences of behavior and/or (b) the modulation of sensorimotor processing so as to bring feedback-guided action under control of appropriate stimuli. To study such complex sequencing or senorimotor function, one requires behavioral dependent variables that contain both centrally-programmed and sensory-guided features. The form and sequence of natural actions used by rats in feeding and grooming have been previously shown to possess identifiable features of both types, and to be well suited to investigation of the neural mechanisms of behavior. The proposed studies employ a set of sensitive ethological measures of behavioral form and sequence to ascertain the effect of striatal lesions and striatal stimulation upon the use of sensory information and central programs to guide action. The results of these studies should help clarify the role of the corpus striatum in guiding behavior. A second goal of the proposed studies is to identify the trigger of a lesion-induced chorea, which preliminary studies have shown to occur under specific conditions. We will also ascertain whether the anti-choreatic agent, haloperidol, can suppress this chorea. The results of this second focus may provide a useful nonprimate model of mechanisms of behavioral chorea.